Substation telephone circuit



Nov."22, 1938. T. s. MARTIN ET AL 2,137,409

SUBSTATION TELEPHONE CIRCUIT Filed NOV. 20, 1930 mm 1; M62 .0 3

Patented Nov. 22, 1938 UNITED STATES T OFFICE ears Talbot G. Martin, Chicago, and Clarence E. Lomax, Oak Park, 111., assignors to Associated Electric Laboratories, poration of Delaware Inc.-, Chicago, 111., a cor- Application November 20, 1933, Serial No. 698,772

13 Claims.

This invention relates in general to substation telephone circuits, "but more particularly to substation telephone circuits for measured service automatic telephone systems, and the principal 5 object is to provide novel and improved circuit arrangements .for metering or charging calls at a substation telephone.

An object of the invention is to provide a substation circuit arrangement in which the telephone subscriber .is compelled to actuate a meter device or deposit a "coin before he can converse with :a called subscriber. In previous arrangements of this kind the calling sub'scribers transmitter was usually disconnected or short circuited by a polarized relay-at the station, which relay was operated by the reversal of battery over the line when the called subscriber responded. .In order to render his transmitter effective the subscriber then had to perform some act to register his call, either actuate a meter or drop a coin in the coin box. In calling an operator where no charge or registration is required, the reversal of battery did not take place and consequently the transmitter was not rendered ineffective. The foregoing arrangement had certain undesirable features.

Itis an object of the present invention to eliminate the relatively sensitive polarized relay and apparatus at the substation and provide instead a more simple and "stable device such as a unidirectional valve or copper oxide rectifier, together with a circuit arrangement embodying a number of novel features.

A further object is to provide an arrangement for automatically restoring the apparatus and circuits at the subscribers station to normal position when the receiver is replaced. 7

An additional object has to do with the means for shunting the rectifiers from the telephone circuit at a time when the calling subscriber is opcrating his calling device to call another station.

A particular feature is concerned with 'a locking push button which upon being actuated by a'subscriber removes the rectifi'ers from the talking circuit and at the same time actuates a charge device; the locked button being subsequently released when the receiver is replaced upon the switchhook.

The invention will be more fully understood from the following detailed description which together with the accompanying drawing illustrates in the usual schematic form a number of preferred embodiments. Fig. l is a circuit of an automatic telephone substation together with certain of the automaticcentral ofiice apparatus;

Fig. 2 is a substation circuit employing a metering device; while Fig. 3 is a substation circuit of a coin collecting telephone.

Referring to Fig. 1, the apparatus at the substation A comprises the usual transmitter '5, re 35 ceiver 6, and the impulse transmitting or calling device l; a switchhook '8 having a number of contact springs l3 and M in the circuit; a combination ringing and talking condenser 9; the ring- H ing coils l0, and the induction coil comprising the secondary winding II and the primary'winding l2. The shunt springs l5 are actuated in the well known manner by the calling device I when impulses are being transmitted. A push button 18 is provided having an extending arm in operative relation with the metering device l9 and a projection engaging the lever spring 20 for controlling contacts '21 and 22. The switchhook 8 is provided with an arm 16 adapted to engage one end of a trigger l1 for releasing the push button if! when thereceiver is replaced. In addition 'to the foregoing apparatus, the substation A is provided with the copper oxide rectifiers 23 and 24, the rectifier 23 being normally poled in the circuit shown so as to be shunted'by the transmitter 5, While the rectifier .24 is poled so as to normally pass current through transmitter 5. The push button i8 upon being actuated operates its contact springs 2B, 21 and 22 to disconnect the rectifier 23 from the circuit of the transmitter, and at the same time the rectifier 24 is shunted.

The line conductors 3|] and 31 extend to the central oflice through the selector switch 'SL and the connector switch ON. The selector SL and connector CN are of well-known construction 35 and comprise 'a groupof relays and associated mechanism for stepping their wipers to a desired level and contact under control 'of the calling device I at the substation A in order to connect with any desired line. These switches together 40 with their wipers have been shown in skeleton 7 form and only the necessary relays and contacts are illustrated so that a full explanation of the invention may be had without unnecessary complication. It is not thought necessary to further describe or show their detail construction and operation, except as will be pointed out. The connector switch CN is shown with its wipers opposite a, set of bank contacts to which line wires and 5| extending to a telephone station Bare 50 connected. A different level of the selector switch SL is shown connected to conductors leading to the operators position C.

A detailed description of thegoperation of the circuit arrangement involved in substation A,

Fig. 1, will now be pointed out. It will be assumed that the subscriber at substation A desires to establish a telephone connection with the subscriber at substation B. His first act is to remove the receiver 6 from the switchhook 8 to thereby, in the well known manner, close contacts I3 and I4 of the switchhook. Contacts I3 close the circuit for the receiver through the secondary winding II of the induction coil to the condenser 9 and across the line conductors 30 and 3|; while the switchhook contacts I4 close the line loop circuit to the selector switch SL for operating the same. The line loop circuit extends from the line relay of the selector (not shown) over the lower line conductor 3 I, primary winding I2 of the induction coil, rectifier 24 which is poled in this direction of current flow while the rectifier 23 opposes it, transmitter 5, the impulse springs of the calling device I, switchhook contacts I4, back over the other side of the line 30 to the line relay again. The subscriber actuates the impulse sender I in a manner to operate the selector switch SL to engage its wipers with the connector CN.

Each time that the calling device 1 is operated to transmit impulses over the line circuit the shunt springs I5 are closed in the well known manner and as long as the calling device is off of its normal position. One pair of the shunt springs I 5 each time closes an obvious shunt path at one point around the transmitter 5 and rectifiers 23 and 24, and another pair of springs at another point close a shunt path around the receiver 6, thereby affording a direct current path clear of impedances for the transmission of the impulses each time the impulse sender is actuated. As soon as the calling device reaches its normal position the shunt springs I5 are again opened to include the transmitter 5, receiver Ii, and rectifiers 23 and 24 in circuit.

When the subscriber A has connected with the connector switch CN preparatory to actuating this switch to the number of the called telephone, the loop circuit extends over a path from ground through the lower winding of line relay 45 of the connector CN, normally closed make before break springs of armature 42, lower line conductor 3| extending through selector SL, primary winding I2 of the induction coil, rectifier 24, which is poled so as to present no opposition to the flow of current in this direction, transmitter 5, impulse springs of the calling device I, switchhook contacts I4, upper line conductor 30, through the selector SL, normally closed make before break contacts of armature 4| of relay 40, through the upper winding of line relay 45 to battery. The impulses operate line relay 45 to control its armature 46 and operate the connector switch CN to step its wipers onto the set of bank contacts connected to line conductors 50 and 5| of the telephone station B. Relay 45 operates over this circuit, but as soon as the impulse sender. I is operated, however, the shunt springs I5 are effective to shunt the substation apparatus as has been pointed out, and a clear impulsing path is afforded.

After the subscriber at substation A has dialled the final digit of the called number to the connector CN, alternating ringing current is automatically transmitted from the connector CN over the line conductors 50 and 5| to operate the ringer at substation B. When the subscriber at substation B responds to the ringing of the bell he removes his receiver from the switchhook and closes a direct current path through his telephone back over line conductors 50 and 5| through the upper and lower windings of re- Versing relay 4!] to battery and ground respectively. Relay 40 energizes and operates its armature spring 4| and 42 to close the normally open contact springs and open its closed springs, thereby completely reversing the connection of battery and ground potential from relay 45 to the line conductors 30 and 3|. Ground is therefore now extended from the lower winding of line relay 45, front contact and armature 42 of relay 40, through the upper line conductor 30 and the selector SL, switchhook contacts I4, impulse springs, of calling device I, rectifier 23 which is poled to assist the current flow in this direction, normally closed contact springs 2| and 22 of push key I8, primary winding I2 of the induction coil, line conductor 3| extending through selector SL, armature 4| and its front contact on relay 40, through the upper winding of relay 45 to battery. The transmitter 5 is shunted from the current path by rectifier 23 and contact springs 2| and 22, while in addition the rectifier 24 will oppose any slight current flow which may take place so as to further render the transmitter 5 ineffective. The subscriber at telephone B may answer in response to this call and he will be heard in the receiver 6 by the subscriber at station A over the secondary current path extending through condenser 9, secondary winding I I of the induction coil, switchhook springsl3, receiver 6, primary winding I2 to the other side of the line so that the subscriber A will be aware that he has established connection with the telephone B.

In order to render his transmitter 5 effective the subscriber at station A must perform some act which will restore his transmitter to operative condition and at the same time charge or meter the call. The push button I 8 is provided for this purpose and the subscriber will actuate this push button and by means of the extension on it operate the meter device I9 to register the call. The movement of the push button I8 at the same time moves the lever spring 20 under the catch of the trigger H, which has previously. been placed in operative position to this spring by the upward movement of the switchhook 8 and extension I6 on it due to the removal of the receiver at the initiating of the call. Push button I8 is therefore locked in its operated position. As a further result of the operation of push button I8 lever spring 20 engages spring 22 while spring 2| is disengaged from spring 22. The rectifier 24 is therefore short circuited by means of lever springs 20 and 22, while the rect fier 23 is completely disconnected from the circuit by the opening of contact springs 2| and 22. A clear talking path is now provided extending over line conductor 30, switchhook contacts I4, impulse springs on calling device I, transmitter 5, lever spring 2|], contact spring 22, primary winding I2 of the induction coil, to the lower line conductor 3|, and over conductors 50 and 5| to the telephone station B. Conversation between the two connected subscribers may now proceed in the usual manner. Current for talking purposes of telephone B being furnished through the windings of relay 40, while that for substation A is furnished through the line relay 45; the condensers 41 and 48 in the connector circuit CN separating these two sources of current, while permitting talking current to flow.

Upon the termination of conversation the subscriber at station A replaces his receiver 6 upon the switchhook :8. This action :opens switchhook contacts I3. and I4 to provide a break in the line conductors 3D and 31 so as to enable the :selector switch SL and connector :swi-tch CN to restore their wipers to normal position in the usual well known manner, which it is not thought necessary .to point :out .in detail as it forms no part of the invention. .As a further result of the operation of the :switchhook ".Biit moves its arm l6 downward on the trigger l1 against the tension of :a :small spring on the trigger, so as to permit the push button I28 and its lever spring 20 to become disengaged from the end of trigger l1 and restore to 'its -normal position. Lever spring 20 thereupon separates from contact spring 22,

while contact springs 2| and '22 again close. The.

substation telephone circuit A is not in its normal position. The relay 40 of connector CN having been .restoredto normal due to the opening of the line circuit, again reverses the battery and ground connection to the line to its original manner preparatory :to receiving further calls.

In certain instances it is desirable for thesub scriber at substation A to call an operator requesting certain information or to call some other person for which no charge is required. In

a situation of this nature the reversal of battery tifier 24, which is poled so as to assist the flow transmitter 4 through contact springs 2| and 22.

The subscriber at substation A therefore need not actuate his push button l8 to meter a call of this nature. Rectifier '24 offers practically no loss to voice currents in this direction of current flow.

Referring now to the modification shown in Fig. 2, the circuit arrangement and the position of the rect'ifiers '23 and 24 in this circuit is precisely the same as that shown in substation A of Fig. '1 with the exception that an additional pair of contacts 32 are provided on push button IS. The magnet 33 is also provided for controlling trigger l1 instead of the switchhook releasing arm 16' as in Fig. 1. In the operation of this circuit the push button IB moves its lever spring '20 behind the trigger guard I! and at the same time operates meter l9. As a further result contact springs 20, 3| and 32 disconnect rectifier 23 and shunt rectifier 24 from transmitter 5, while at contacts 32 a circuit is prepared for releasing magnet 33 over one side of the line 30. The magnet 33, however, is prevented from operating at this time due to the shunt circuit around it extending over the switchhook 8 and its contacts l4. When the receiver 1 is replaced on the hookswitch 8 upon the termination of a call, contact springs 14 are opened and magnet 33 is included in the line circuit. It thereupon energizes over the line circuit and contact springs 32, and operates the trigger I? so as to disengage it from lever spring 20 and permit restoration of push button 18. Contact 32 is thereby opened .80 as to disconnect magnet 33 i-rom the circuit. The mechanism is now restored to its normal position. This arrangement lends itself so that the rectifiers, push button and magnet .33 may be mounted at some point exterior of the bell box containing the remaining equipment. In the foregoing circuit arrangement the rectifiers 23 and 2d operate in the same manner as described in connection with Fig. 1

to control the circuit of the transmitter 5, and a detail explanation of the manner in which this is accomplished is not thought necessary.

Referring now to Fig. 3, this shows a substation circuit applied to a coin collect telephone employing a circuit arrangement exactly the same as that of Fig. 2. Instead of providing a push button, however, a curved extension is' formed on the lever spring 29 which projection extends a short distance into the coin slot 36 so that it can be actuated by the passing, of a coin 35 in its path through the coin chute 36 to the collect receptacle. The coin 35 is dropped into the slot '36 when the response of the called party is heard by the subscriber in his receiver. The coin in striking the curved projection of lever spring 20 operates contacts 20, 2|, 22 and 32 and locks the said springs under control of trigger l'l. ihe action of the rectifiers 23 and 24 in controlling the circuit through transmitter is the same as has been pointed out heretofore. The contacts 32 prepare a circuit for magnet 33 so that this magnet will energize as soon as the receiver is replaced on the switchhook l8 to open contacts l4. The trigger ll restores the set of contact springs 26, 2|, 22 and -32 and permits the curved extension on lever spring 20 to again enter the coin slot 36. The other operations are the same as before.

Having described the invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What is claimed is: r

1. In a substation telephone circuit, telephone apparatus, a pair of rectifiers, one of said rectifiers normally connected in shunt and the other rectifier in series with said telephone apparatus, and circuit controlling means in the telephone circuit for removing said rectifiers from the circuit of said telephone apparatus.

2. In a substation telephone circuit, telephone apparatus, a pair of rectifiers, one of said rectifiers connected normally in shunt with said telephone apparatus and the other rectifier in series, and circuit controlling means in the telephone circuit operated for disconnecting said first rectifier from said telephone apparatus and shunting said second rectifier.

3. In a substation telephone circuit, telephone apparatus, rectifying means connected in circuit of said telephone apparatus to render it inoperative When a connection is established with another telephone, a locking push button for removing saidrectifying means from said circuit to render said telephone apparatus operative, and means for unlocking said push button.

.4. In a telephone system, a calling and a called telephone, means for establishing a connection between said telephones, a rectifier connected in series with said calling telephone, means responsive to the answering of said called telephone for transmitting current to said calling telephone through said rectifier in a direction to shunt the calling telephone, and means in said calling telephone for disconnecting said rectifier to render the calling telephone operative.

5. In a telephone system, a calling and a called telephone, rectifying means connected in the circuit of said calling telephone, means for establishing a connection between said telephones over a current path passing through said rectifying means, means responsive to the answering of the called telephone for establishing a reverse current path to said calling telephone opposed by said rectifying means so as to render the calling telephone inoperative, and a push button at said calling telephone for removing said rectifying means from said circuit to render the calling telephone operative.

6. In a telephone system, a calling and a called substation telephone circuit, rectifying means at said calling telephone, an operators circuit, means for establishing a telephone connection between said substation circuits, means responsive to said connection for extending current to said calling telephone through said rectifying means to render the apparatus thereat inoperative, means at said calling telephone for removing said rectifying means from the circuit to render the calling apparatus operative, means for establishing a telephone connection between said calling telephone and said operators circuit, and means responsive to the connection with said operators circuit for extending current to said calling telephone through said rectifying means without rendering said calling telephone inoperative.

7. In a telephone system, a calling and a called substation, an operators position, rectifying means at said calling station, means for establishing a telephone connection between said calling substation and said operators position from a current source extending through said rectifying means in a direction to render said calling telephone operative, means for establishing a telephone connection between said calling and said called substations from a current source extending through said rectifying means in a reversed direction to render said calling telephone inoperative, means at said calling telephone for disconnecting said rectifying means to render the telephone again operative and for registering the call, and means responsive to the disconnection of said telephone connection for restoring said rectifying means to its initial position in the calling telephone.

8. In a substation telephone circuit, an impulse sender, a transmitter and a receiver in said circuit, rectifying means in said circuit for controlling the circuit of said transmitter, and means controlled by the operation of said impulse sender for shunting said transmitter, receiver and rectifying means.

9. In a substation telephone circuit, an impulse sender, shunt springs controlled by said impulse sender, a transmitter and a receiver in said circuit, rectifying means for controlling the circuit of said transmitter, and means responsive to the operation'of said impulse sender'for operating said shunt springs to shunt said transmitter, said receiver and said rectifying means from said telephone circuit during the transmission of impulses.

10. In a substation telephone circuit, an impulse sender, shunt springs controlled by said impulse sender, a transmitter and a receiver in said circuit, a pair of rectifiers, one of said rectifiers connected in shunt of said transmitter and the other one in series therewith, said shunt springs operated by said impulse sender during the transmission of impulses over said telephone circuit to short'circuit said transmitter, said receiver and said rectifiers from said impulsing circuit, and means for disconnecting said shunt rectifier from said transmitter and for short circuiting said series rectifier therefrom independent of said shunt springs and while said impulse sender is at rest.

11. In a telephone system, a calling substation telephone, a transmitter including rectifying means for controlling the same, said transmitter rendered inoperative by said rectifying means when a telephone call is made from said calling telephone, a locking key controlling the circuit of said rectifying means, said key operated to remove the control of said rectifying means from said transmitter and to make a registration of the call, and a release magnet operated responsive to the disconnection of said call for unlocking said key.

12. A telephone set comprising a microphone, a circuit therefor, a rectifier in said circuit in series with said microphone, a rectifier in said circuit in parallel with said microphone and said first mentioned rectifier, and means operative upon payment for shunting the rectifier in series with the microphone and for opening the connection in said circuit for the rectifier in parallel with the microphone.

13. In a telephone pay station, a microphone, two rectifiers, pulsing and off-normal dial contacts, 'switchhook contacts, coin operated contacts, a circuit arrangement for establishing a talking connection effective on the operation of the switchhook contacts, a circuit arrangement for establishing a dialing connection efiective on the operation of the off-normal contacts, a, circuit arrangement effective on the reversal of current to the pay station for preventing a current passing through the microphone, said circuit arrangement including one rectifier blocking the passage of said current through the microphone and the other rectifier by-passing said current past the microphone, and a circuit arrangement effective on the operation of the coin operated contacts for establishing a talking connection through the microphone without again reversing the current.

TALBOT G. MARTIN. CLARENCE E. LOMAX. 

